What is your opinion on any of the half-dozen topics briefly touched on in the article?
If these exchanges are providing best execution by filling orders with "high frequency traders" operating in these pools of the damned, then I don't see an issue. If the pay for deal flow arrangements aren't in the best interest of the client, then there's an issue.
Personally, I don't understand the fuss over high frequency trading. If you want to try and grind out fractions of a penny by front running on the investment decisions of others then good !@#$ing luck. It can and does generate money but coupled with less efficient pricing and increasing volatility, its getting more and more risky. You're asking for trouble.
Market pricing has become less efficient naturally since the crash in 2008. Funds have shifted away from active investors into more passive strategies. The rise of ETF's has really hurt active investors and by extension pricing efficiency. The constant re-balancing has also increased volatility. That sounds scary, but where there's inefficiency there's opportunity for fundamental and value investors.
I don't think we are nearing a point where our markets are at risk of losing integrity. I expect a shift back to active managers down the line as market efficiency creates opportunity and above market gains for active strategies.